In recent years, a user terminal (so-called dual terminal) comprising a cellular communication unit and a wireless LAN communication unit is becoming widely used. Further, the number of wireless LAN access points (hereinafter called “access points”) managed by an operator of a cellular communication system increases.
Therefore, in 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a cellular communication system, it is expected to consider a technology capable of enhancing cooperation between a cellular communication system and a wireless LAN system (see Non Patent Document 1).
One purpose of such technology is that balance of load level in a cellular base station and an access point is taken by improving usage rate of access point.
For example, it is possible to transfer (offload) traffic load of a cellular base station to an access point by switch such that traffic transmitted and received between the cellular base station and a user terminal is transmitted and received between the access point and the user terminal.